Procedure:

. Preparing 20 ml of saturated solution of sodium bicarbonate with the sample solution.

. 2.5 ml of the above solution was taken in a test tube with a calibrated Pasteur pipette.

. Adding 1 drop of starch indicator to the tube and stir well.
. Adding KI + I2 solution drop wise with another pipette till a blue colour of the solution appears.

. Count the number of drops of KI + I2 solution used.